1. Field of the Invention
The present invention is directed to a tennis ball projecting device which is operated by computer and can vary and control the trajectory, placement, speed, spin, and timing of the projected balls.
2. Description of the Related Art
Devices for projecting balls are well known in the art.
U.S. Pat. No. 5,123,643 to Heilhecker et al teaches an apparatus which will fling a ball from a pouch powered by elastic straps. There is no disclosed manner to accurately adjust the timing of delivery of the propelled balls using this device.
U.S. Pat. No. 4,335,701 to Bozich teaches propelling a baseball by striking the ball with a plunger. All functions are manually controlled, eliminating the advantage of a single player practicing alone.
U.S. Pat. No. 4,193,591 to Paulson; U.S. Pat. No. 4,197,827 to Smith; RE30,703 to Paulson et al; U.S. Pat. No. 4,323,047 to McIntosh et al; U.S. Pat. No. 4,325,351 to Yuasa; U.S. Pat. No. 5,125,653 to Kovacs et al (the most closely related prior art known by the inventor); U.S. Pat. No. 4,442,823 to Floyd et al; U.S. Pat. No. 5,044,350 to Iwabuchi et al; U.S. Pat. No. 5,464,208 to Pierce; U.S. Pat. No. 5,178,123 to Yeh; U.S. Pat. No. 5,195, 744 to Kapp et al; and U.S. Pat. No. 5,437,261 to Paulson et al propel the ball by capturing the ball on the proximal side of two wheels which are spinning in opposite directions and using the acquired centrifugal force to propel the ball out the distal side of the wheels. The use of this method of propulsion causes a marked degradation in impact point reliability due to balls of different surface wear, diameter, and compression. Another disadvantage of the spinning wheels mode of propulsion is the accumulation around the machine of an annoying amount of fuzz from the balls. The greatest drawback to creating a realistic tennis game which is created by this method of propulsion is the difficulty of firing successive balls with an extreme difference in projection parameters within a realistic timing lapse. As an example, a timing lapse of 2.4 seconds between a hard base-line or passing shot followed by a drop shot or lob calls for a much slower velocity of the ball and requires the spinning wheels to spool down so drastically that consistency or accuracy is virtually impossible. Also, the placement of balls under identical conditions lacks consistency.
U.S. Pat. No. 3,989,245 to Augustine, Jr. et al is drawn to a computerized device for pneumatically projecting tennis balls. This device is to be used with a specially constructed enclosed court to allow ball retrieval. After the ball is introduced by a small rotating injector into the long, complicated bent tube, it is accelerated along its passage by three separate compressed air orifices, each with its own control unit. Therefore, there is no build-up of pressure behind the ball prior to its release. It is taught that the pressure regulator may be manually controlled.
U.S. Pat. No. 4,291,665 is an example of an early type of pneumatic propulsion devices for tennis balls. The machine may be programmed to oscillate from side to side. The trajectory of the balls and the location of the impact of the balls must be set by hand while the machine is inactive. The speed of the carousel governs the timing of the committed ball to proceed to a rubber bladder from which it is ejected after the build-up of a sufficient, unalterable air pressure. Thus, there is little control over the timing of the balls and the speed of the balls leaving the device.
U.S. Pat. No. 5,496,025 to Phillips et al is directed to a pneumatic device for propelling balls of different sizes. The barrels are of different sizes for holding different sized balls. The device has a single air pressure control valve which is set manually. Apparently, the device can propel a tennis ball every 5 seconds. This time is too great if a realistic game-type situation is desired.
U.S. Pat. No. 5,257,615 to Jones teaches a pneumatic device for the propulsion of tennis balls. This device suffers from the limitation of having no controlled elevational or lateral direction capability or sequential variability. Thus, the simulation of an actual game is impossible.
U.S. Pat. No. 3,989,027 to Kahelin describes a pneumatic device for propelling balls of varying diameters. It has manually changeable barrels. Timing and pressure changes must be made manually. Directing pressure from the tank to the firing chamber is complicated in that a piston-activated sliding sleeve must be utilized to choke off air vents.
U.S. Pat. No. 5,107,820 to Salansky displays improved features over many of the aforementioned prior art devices. One of the goals of this invention is to match the pauses between the balls that are fired to the trajectory characteristics established by the firing system so that they are in keeping with an actual game of tennis. This is hoped to be accomplished by controlling the feed sequence (and thus of course, the firing sequence frequency). Thus a pause following a low, fast ball is brief, and longer after a high ball. This apparatus gives the player a more pronounced feeling that he is playing, not against a machine that delivers balls with a regular rhythm, but against live opponents. This machine uses the spinning wheels system of propulsion and is thus subject to the disadvantages enumerated earlier which are inherent in such systems. Additionally, the timing of the firing of a particular ball is directly linked to the feeder. The patent states that a variable feed sequence of the feed system is controlled as a function of the firing settings of the ball firing system. Thus the timing system of the Salansky system depends on controlling the time between ball drops from the holding mechanism. The dropped balls are then caught by the spinning wheels and propelled out of the machine. Whereas this is an improvement over other machines which have been discussed, the timing is not as precise as could be desired due to the difference in timing which occurs between dropped balls being caught by the spinning wheels.
U.S. Pat. No. 4,233,953 to Bash is indicated as being an add-on to existing machines, this device incorporates direct linkages of the rotary distributor with the discharge system and a ball fires when it drops from the hopper through an opening into the chamber and passes through a bladder (arresting device) after the build-up of sufficient pressure. The only new feature disclosed is the possibility of a manual setting of the limits of the lateral oscillation of the mechanism. As mentioned above, manual operation eliminates the possibility of a single player engaging in a realistic game.
U.S. Pat. No. 4,570,607 to Stokes discloses a pneumatic device for propelling tennis balls. The gist of the invention is a barrel which has an orbital motion and which rotates. The novelty of design consists of an unusual way to induce spin. A strip of Velcro is attached to one inner side of the tube to induce spin. Thus there is no possibility of propelling a ball without spin. Also, the elevation of the tube must be set manually.
While the above discussion is not exhaustive of the prior art devices which are stated to be useful for propelling balls, it is sufficient to point out a number of the problems existing in the art. It is the purpose of the present invention to maintain the beneficial aspects of the better devices disclosed in the prior art while overcoming their flaws.